Thursday, July 15, 2010

A new study published in Proceedings of the National Academy of Sciences reveals differing hormone levels in our two closest relatives, bonobos and chimpanzees, in anticipation of competition.

Chimpanzees live in male-dominated societies where status is paramount and aggression can be severe. In bonobos, a female is always the most dominant and tolerance can allow for more flexible cooperation and food-sharing.

Scientists have frequently questioned whether differences in competitive behavior could in part be explained by differing physiological responses to competition. In their new study, researchers from Harvard and Duke collected saliva from the apes using cotton wads dipped in Sweet Tarts candy, then measured hormone levels before and after pairs from each species were presented with a pile of food.

They found that males of both species who were intolerant and could not share with their partners showed hormonal changes in anticipation of competing for the food, but bonobos and chimpanzees were completely different in which hormones increased.

Male chimpanzees showed an increase in testosterone, which is thought to prepare animals for competition or aggressive interactions. By contrast, male bonobos showed an increase in cortisol, which is associated with stress and more passive social strategies in other animals.

"Chimpanzee males reacted to the competition as if it was a threat to their status, while bonobos reacted as if a potential competition is stressful by showing changes in their cortisol levels," said Victoria Wobber, a Harvard graduate student and first author of the study.

Human males usually experience an increase in cortisol before many types of competition in a similar way as seen in the bonobos. However, if men have what is called a "high power motive," or a strong desire to achieve high status, they experience an increase in testosterone before a competition.

"These results suggest that the steroid hormone shifts that are correlated with the competitive drive of men are shared through descent with other apes," Wobber said.

While some men may seem more bonobo-like before competition and others more chimpanzee-like, something unique about human males is that after competition they experience an increase in testosterone if they win or a decrease in testosterone if they lose -- which accounts for giddy or depressed sports fans following a win or loss. This variation in hormones post-competition was not observed in either chimpanzees or bonobos.

"It's exciting because we can see that in some ways we're similar to bonobos, in others we're similar to chimpanzees," said Duke anthropologist Brian Hare, co-author. "But then there's also a part of our biology that seems to be entirely unique."

Whether mom's golden child or her black sheep, siblings who sense that their mother consistently favors or rejects one child over others are more likely to show depressive symptoms as middle-aged adults, finds a new study by Cornell gerontologist Karl Pillemer.

Prior research has shown that parental favoritism among siblings negatively affects mental health and often triggers behavioral problems in children, teens and young adults, but the survey of 275 Boston-area families, co-directed by Purdue sociologist Jill Suitor, is the first to show that such harmful effects persist long into adulthood.

"Perceived favoritism from one's mother still matters to a child's psychological well-being, even if they have been living for years outside the parental home and have started families of their own," said Pillemer, the Hazel E. Reed Professor in the Department of Human Development and associate dean for extension and outreach in the College of Human Ecology, about his paper in the Journal of Marriage and Family (April 2010).

"It doesn't matter whether you are the chosen child or not, the perception of unequal treatment has damaging effects for all siblings," he added. "The less favored kids may have ill will toward their mother or preferred sibling, and being the favored child brings resentment from one's siblings and the added weight of greater parental expectations."

Favoritism may be difficult for mothers to avoid, however, as the researchers found that 70 percent of moms surveyed named a child to whom they felt closest and only 15 percent of children saw equal treatment by their mothers. Similarly, 92 percent of children and 73 percent of mothers specified a child with whom the mother battled most frequently.

The study, which controlled for family size, race and other factors, drew on interviews with 275 mothers in their 60s and 70s with at least two living adult children and also surveys of 671 offspring of the women. In addition to questions about emotional closeness or excessive conflict with a particular child, mothers and children were asked about the mother's expectations for who will care for her when she becomes ill or disabled. When mothers designated a child as her caregiver, all children suffered greater depressive symptoms, though the children's perceptions of their mother's preference did not relate to their mental health.

The findings could lead to new therapies for practitioners who work with later-life families, Pillemer said. "We have a powerful norm in our society that parents should treat kids equally, so favoritism can be something of a taboo topic. If counselors can help older parents and adult children bring some of these issues into the open, it may help prevent family conflict from arising."

In addition to Suitor, other co-authors include Charles Henderson, senior research associate in human development, and Ph.D. student Seth Pardo, both of Cornell.

To the untrained eye, University of Colorado at Boulder Research Associate Craig Lee's recent discovery of a 10,000-year-old wooden hunting weapon might look like a small branch that blew off a tree in a windstorm.

Nothing could be further from the truth, according to Lee, a research associate with CU-Boulder's Institute of Arctic and Alpine Research who found the atlatl dart, a spear-like hunting weapon, melting out of an ice patch high in the Rocky Mountains close to Yellowstone National Park.

Lee, a specialist in the emerging field of ice patch archaeology, said the dart had been frozen in the ice patch for 10 millennia and that climate change has increased global temperatures and accelerated melting of permanent ice fields exposing organic materials that have long been entombed in the ice.

"We didn't realize until the early 2000s that there was a potential to find archaeological materials in association with melting permanent snow and ice in many areas of the globe," Lee said. "We're not talking about massive glaciers, we're talking about the smaller, more kinetically stable snowbanks that you might see if you go to Rocky Mountain National Park."

As glaciers and ice fields continue to melt at an unprecedented rate, increasingly older and significant artifacts -- as well as plant material, animal carcasses and ancient feces -- are being released from the ice that has gripped them for thousands of years, he said.

Over the past decade, Lee has worked with other researchers to develop a geographic information system, or GIS, model to identify glaciers and ice fields in Alaska and elsewhere that are likely to hold artifacts. They pulled together biological and physical data to find ice fields that may have been used by prehistoric hunters to kill animals seeking refuge from heat and insect swarms in the summer months.

"In these instances, what we're finding as archaeologists is stuff that was lost," Lee said. "Maybe you missed a shot and your weapon disappeared into the snowbank. It's like finding your keys when you drop them in snow. You're not going to find them until spring. Well, the spring hasn't come until these things started melting for the first time, in some instances, in many, many thousands of years."

The dart Lee found was from a birch sapling and still has personal markings on it from the ancient hunter, according to Lee. When it was shot, the 3-foot-long dart had a projectile point on one end, and a cup or dimple on the other end that would have attached to a hook on the atlatl. The hunter used the atlatl, a throwing tool about two feet long, for leverage to achieve greater velocity.

Later this summer Lee and CU-Boulder student researchers will travel to Glacier National Park to work with the Salish, Kootenai and Blackfeet tribes and researchers from the University of Wyoming to recover and protect artifacts that may have recently melted out of similar locations.

"We will be conducting an unprecedented collaboration with our Native American partners to develop and implement protocols for culturally appropriate scientific methods to recover and protect artifacts we may discover," he said.

Quick retrieval of any organic artifacts like clothing, wooden tools or weapons is necessary to save them, because once thawed and exposed to the elements they decompose quickly, he said.

An estimated 10 percent of Earth's land surface is covered with perennial snow, glaciers and ice fields, providing plenty of opportunities for exploration, Lee said. However, once organic artifacts melt out of the ice, they could be lost forever.

"Ninety-five percent of the archaeological record that we usually base our interpretations on is comprised of chip stone artifacts, ground stone artifacts, maybe old hearths, which is a fire pit, or rock rings that would have been used to stabilize a house," Lee said. "So we really have to base our understanding about ancient times on these inorganic materials. But ice patches are giving us this window into organic technology that we just don't get in other environments."

A new study shows the Arctic climate system may be more sensitive to greenhouse warming than previously thought, and that current levels of Earth's atmospheric carbon dioxide may be high enough to bring about significant, irreversible shifts in Arctic ecosystems.

Led by the University of Colorado at Boulder, the international study indicated that while the mean annual temperature on Ellesmere Island in the High Arctic during the Pliocene Epoch 2.6 to 5.3 million years ago was about 34 degrees Fahrenheit, or 19 degrees Celsius, warmer than today, CO2 levels were only slightly higher than present. The vast majority of climate scientists agree Earth is warming due to increased concentrations of heat-trapping atmospheric gases generated primarily by human activities like fossil fuel burning and deforestation.

The team used three independent methods of measuring the Pliocene temperatures on Ellesmere Island in Canada's High Arctic. They included measurements of oxygen isotopes found in the cellulose of fossil trees and mosses that reveal temperatures and precipitation levels tied to ancient water, an analysis of the distribution of lipids in soil bacteria which correlate with temperature, and an inventory of ancient Pliocene plant groups that overlap in range with contemporary vegetation.

"Our findings indicate that CO2 levels of approximately 400 parts per million are sufficient to produce mean annual temperatures in the High Arctic of approximately 0 degrees Celsius (32 degrees F)," Ballantyne said. "As temperatures approach 0 degrees Celsius, it becomes exceedingly difficult to maintain permanent sea and glacial ice in the Arctic. Thus current levels of CO2 in the atmosphere of approximately 390 parts per million may be approaching a tipping point for irreversible ice-free conditions in the Arctic."

A paper on the subject is being published in the July issue of the journal Geology. Co-authors included David Greenwood of Brandon University in Manitoba, Canada, Jaap Sinninghe Damste of the Royal Netherlands Institute for Sea Research, Adam Csank of the University of Arizona, Natalia Rybczynski of the Canadian Museum of Nature in Ottawa and Jaelyn Eberle, curator of fossil vertebrates at the University of Colorado Museum of Natural History and an associate professor in the geological sciences department. Arctic temperatures have risen by about 1.8 degrees F, or 1 degree C, in the past two decades in response to anthropogenic greenhouse warming, a trend expected to continue in the coming decades and centuries, said Ballantyne. Greenhouse gases in the atmosphere have risen from about 280 parts per million during the pre-industrial era on Earth to about 390 parts per million today.

During the Pliocene, Ellesmere Island hosted forests of larch, dwarf birch and northern white cedar trees, as well as mosses and herbs, including cinquefoils. The island also was home to fish, frogs and now extinct mammals that included tiny deer, ancient relatives of the black bear, three-toed horses, small beavers, rabbits, badgers and shrews. Because of the high latitude, the Ellesmere Island site on the Strathcona Fiord was shrouded by darkness six months out of the year, said Rybczynski.

Fossils are often preserved in a process known as permineralization, in which mineral deposits form internal casts of organisms. But at the Ellesmere Island site known as the "Beaver Pond site," organic materials -- including trees, plants and mosses -- have been "mummified" in peat deposits, allowing the researchers to conduct detailed, high-quality analyses, said Eberle.

Ballantyne said the high level of preservation of trees and mosses at Ellesmere Island allowed the team to measure the ratio of oxygen isotopes in plant cellulose, providing information on water absorbed from precipitation during the Pliocene and which yielded estimates of past surface temperatures. The team also compared data on the width of tree rings in larch trees at the Beaver Pond site to trees at lower latitudes today to help them estimate past temperatures and precipitation levels.

The researchers also analyzed the distribution of ancient membrane lipids from soil bacteria known as tetraethers, which correlate to temperature. The chemical structure of the fossilized tetraethers makes them highly sensitive to both temperature and acidity, or pH, said Ballantyne.

The last line of evidence put forward by the CU-Boulder-led team was a comparison of Pliocene ancient vegetation at the site with vegetation present today, providing a clear "climate window" showing the overlap of the two time periods. "The results of the three independent temperature proxies are remarkably consistent," said Eberle. "We essentially were able to ‘read' the vegetation in order to estimate air temperatures in the Pliocene."

Today, Ellesmere Island is a polar desert that features tundra, permafrost, ice sheets, sparse vegetation and a few small mammals. Temperatures range from roughly minus 37 degrees F, or minus 38 degrees C, in winter to 48 degrees F, or 9 degrees C, in summer. The region is one of the coldest, driest environments on Earth.

"Our findings are somewhat disconcerting regarding the temperatures and greenhouse gas levels during the Pliocene," said Eberle. "We already are seeing evidence of both mammals and birds moving northward as the climate warms, and I can't help but wonder if the Arctic is headed toward conditions similar to those that existed during the Pliocene."

Elevated Arctic temperatures during the Pliocene -- which occurred shortly before Earth plunged into an ice age about 2.5 million years ago -- are thought to have been driven by the transfer of heat to the polar regions and perhaps by decreased reflectivity of sunlight hitting the Arctic due to a lack of ice, said Ballantyne. One big question is why the Arctic was so sensitive to warming during this period, he said.

Multiple feedback mechanisms have been proposed to explain the amplification of Arctic temperatures, including the reflectivity strength of the sun on Arctic ice and changes in vegetation seasonal cloud cover, said Ballantyne. "I suspect that it is the interactions between these different feedback mechanisms that ultimately produce the warming temperatures in the Arctic."

In 2009, CU-Boulder's National Snow and Ice Data Center showed the September Arctic sea ice extent was 649,000 square miles, or 1,680,902 square kilometers, below the 1979-2000 average, and is declining at a rate of 11.2 percent per decade. Some climate change experts are forecasting that the Arctic summers will become ice-free summers within a decade or two.

In addition to its exceptional preservation of fossil wood, plants, insects and mollusks, the Beaver Pond site on Ellesmere Island is the only reported Pliocene fossil site in the High Arctic to yield vertebrate remains, said Rybczynski.

Eberle said there is high concern by scientists over a proposal to mine coal on Ellesmere Island near the Beaver Pond site by WestStar Resources Inc. headquartered in Vancouver, British Columbia. "Paleontological sites like the Beaver Pond site are unique and extremely valuable resources that are of international importance," said Eberle. "Our concern is that coal mining activities could damage such sites and they will be lost forever."

Many of the Milky Way’s ancient stars are remnants of other smaller galaxies torn apart by violent galactic collisions around five billion years ago, according to researchers at Durham University, who publish their results in a new paper in the journal Monthly Notices of the Royal Astronomical Society.

Scientists at Durham’s Institute for Computational Cosmology and their collaborators at the Max Planck Institute for Astrophysics, in Germany, and Groningen University, in Holland, ran huge computer simulations to recreate the beginnings of our Galaxy.

The simulations revealed that the ancient stars, found in a stellar halo of debris surrounding the Milky Way, had been ripped from smaller galaxies by the gravitational forces generated by colliding galaxies.

Cosmologists predict that the early Universe was full of small galaxies which led short and violent lives. These galaxies collided with each other leaving behind debris which eventually settled into more familiar looking galaxies like the Milky Way.

The researchers say their finding supports the theory that many of the Milky Way’s ancient stars had once belonged to other galaxies instead of being the earliest stars born inside the Galaxy when it began to form about 10 billion years ago.

Lead author Andrew Cooper, from Durham University’s Institute for Computational Cosmology, said: “Effectively we became galactic archaeologists, hunting out the likely sites where ancient stars could be scattered around the galaxy.

“Our simulations show how different relics in the Galaxy today, like these ancient stars, are related to events in the distant past.

“Like ancient rock strata that reveal the history of Earth, the stellar halo preserves a record of a dramatic primeval period in the life of the Milky Way which ended long before the Sun was born.”

The computer simulations started from shortly after the Big Bang, around 13 billion years ago, and used the universal laws of physics to simulate the evolution of dark matter and the stars.

These simulations are the most realistic to date, capable of zooming into the very fine detail of the stellar halo structure, including star “streams” – which are stars being pulled from the smaller galaxies by the gravity of the dark matter.

One in one hundred stars in the Milky Way belong to the stellar halo, which is much larger than the Galaxy’s familiar spiral disk. These stars are almost as old as the Universe.

The first experimental evidence showing how atmospheric nitrogen can be incorporated into organic macromolecules is being reported by a University of Arizona team. The finding indicates what organic molecules might be found on Titan, the moon of Saturn that scientists think is a model for the chemistry of pre-life Earth.

Earth and Titan are the only known planetary-sized bodies that have thick, predominantly nitrogen atmospheres, said Hiroshi Imanaka, who conducted the research while a member of UA's chemistry and biochemistry department.

How complex organic molecules become nitrogenated in settings like early Earth or Titan's atmosphere is a big mystery, Imanaka said.

"Titan is so interesting because its nitrogen-dominated atmosphere and organic chemistry might give us a clue to the origin of life on our Earth," said Imanaka, now an assistant research scientist in the UA's Lunar and Planetary Laboratory. "Nitrogen is an essential element of life."

However, not just any nitrogen will do. Nitrogen gas must be converted to a more chemically active form of nitrogen that can drive the reactions that form the basis of biological systems.

Imanaka and Mark Smith converted a nitrogen-methane gas mixture similar to Titan's atmosphere into a collection of nitrogen-containing organic molecules by irradiating the gas with high-energy UV rays. The laboratory set-up was designed to mimic how solar radiation affects Titan's atmosphere.

Most of the nitrogen moved directly into solid compounds, rather than gaseous ones, said Smith, a UA professor and head of chemistry and biochemistry. Previous models predicted the nitrogen would move from gaseous compounds to solid ones in a lengthier stepwise process.

Titan looks orange in color because a smog of organic molecules envelops the planet. The particles in the smog will eventually settle down to the surface and may be exposed to conditions that could create life, said Imanaka, who is also a principal investigator at the SETI Institute in Mountain View, Calif.

However, scientists don't know whether Titan's smog particles contain nitrogen. If some of the particles are the same nitrogen-containing organic molecules the UA team created in the laboratory, conditions conducive to life are more likely, Smith said.

Laboratory observations such as these indicate what the next space missions should look for and what instruments should be developed to help in the search, Smith said.

Imanaka and Smith's paper, "Formation of nitrogenated organic aerosols in the Titan upper atmosphere," is scheduled for publication in the Early Online edition of the Proceedings of the National Academy of Sciences the week of June 28. NASA provided funding for the research.

Therefore, Imanaka and Smith used the Advanced Light Source at Lawrence Berkeley National Laboratory's synchroton in Berkeley, Calif. to shoot high-energy UV light into a stainless steel cylinder containing nitrogen-and-methane gas held at very low pressure.

The researchers used a mass spectrometer to analyze the chemicals that resulted from the radiation.

Simple though it sounds, setting up the experimental equipment is complicated. The UV light itself must pass through a series of vacuum chambers on its way into the gas chamber.

Many researchers want to use the Advanced Light Source, so competition for time on the instrument is fierce. Imanaka and Smith were allocated one or two time slots per year, each of which was for eight hours a day for only five to 10 days.

For each time slot, Imanaka and Smith had to pack all the experimental equipment into a van, drive to Berkeley, set up the delicate equipment and launch into an intense series of experiments. They sometimes worked more than 48 hours straight to get the maximum out of their time on the Advanced Light Source. Completing all the necessary experiments took years.

It was nerve-racking, Imanaka said: "If we miss just one screw, it messes up our beam time."

At the beginning, he only analyzed the gases from the cylinder. But he didn't detect any nitrogen-containing organic compounds.

Imanaka and Smith thought there was something wrong in the experimental set-up, so they tweaked the system. But still no nitrogen.

"It was quite a mystery," said Imanaka, the paper's first author. "Where did the nitrogen go?"

Finally, the two researchers collected the bits of brown gunk that gathered on the cylinder wall and analyzed it with what Imanaka called "the most sophisticated mass spectrometer technique."

Imanaka said, "Then I finally found the nitrogen!"

Imanaka and Smith suspect that such compounds are formed in Titan's upper atmosphere and eventually fall to Titan's surface. Once on the surface, they contribute to an environment that is conducive to the evolution of life.